Ruth May Tunnicliff (May 1, 1876 – September 22, 1946) was an American physician, medical researcher, bacteriologist, and pathologist, based in Chicago.

She developed a serum against measles, and did laboratory research for the United States Army during the 1918 influenza pandemic.

[5] Tunnicliff was a research bacteriologist at the John McCormick Memorial Institute for Infectious Diseases.

[1][3][7] During World War I, she held the title "Contract Surgeon" with the United States Army,[8][9] and worked at Camp Pike in Little Rock, Arkansas, and Camp George Meade in Maryland, during the 1918 influenza pandemic.

[24] Ruth Tunnicliff died in 1946, aged 70 years, in Chicago.